1. Field of the Invention
The present invention relates to a deposition apparatus used for depositing a material which is capable of being deposited over a substrate, and a manufacturing apparatus provided with the deposition apparatus. The present invention also relates to a deposition method using the deposition apparatus. The present invention also relates to a light-emitting device including an organic compound-containing layer, which is formed using the deposition apparatus, as a light-emitting layer, and a manufacturing method of the light-emitting device.
2. Description of the Related Art
A light-emitting element using, as a luminous body, an organic compound which has characteristics such as thinness, lightness in weight, high-speed response, and DC drive at low voltage, is expected to be applied to a next-generation flat panel display. In particular, a display device in which light-emitting elements are arranged in matrix is considered to have an advantage in a wide viewing angle and excellent visibility over a conventional liquid crystal display device.
A light-emitting element is said to have an emission mechanism in which by application of voltage to a pair of electrodes with an organic compound-containing layer interposed therebetween, electrons injected from a cathode and holes injected from an anode are recombined in an emission center of the organic compound-containing layer to form molecular excitons and the molecular excitons release energy in returning to a ground state; accordingly light is emitted. As excited states, a singlet excited state and a triplet excited state are known, and light emission is considered to be possible through either of these excited states.
For a light-emitting device in which such light-emitting elements are arranged in matrix, a driving method such as passive matrix driving (simple matrix type) or an active matrix driving (active matrix type) can be used. However, when the pixel density is increased, the active matrix type where each pixel (or each dot) is provided with a switch is considered to be advantageous because it is capable of lower voltage driving.
The organic compound-containing layer has a structure typified by a stacked structure of a hole transporting layer, a light-emitting layer, and an electron transporting layer. As a deposition method of these organic compound material, an ink jet method, an evaporation method, a spin coating method, or the like are known. EL materials for forming EL layers are broadly classified into low molecular (monomer) materials and high molecular (polymer) materials. An evaporation apparatus is used for depositing low molecular materials.
In a conventional evaporation apparatus, a substrate is set on a substrate holder, and a crucible (or an evaporation boat) which contains an EL material, that is, an evaporation material, a shutter for preventing the rise of the EL material to be sublimated, and a heater for heating the EL material in the crucible are included. The EL material heated by the heater is sublimated to be deposited on a rotating substrate. At this time, the substrate and the crucible are kept from each other with a distance of greater than or equal to one meter for uniform deposition.
When manufacture of a full-color flat panel display using emission colors of red, green, and blue is considered, because the accuracy of deposition is not so high, pixels are designed so as to have wide intervals therebetween, or an insulator called a bank is provided between the pixels.
Demands such as higher definition, higher opening aperture, and higher reliability on a full-color flat panel display using emission colors of red, green, and blue have been increased. Such demands are big objects in advancing higher definition (increase in the number of pixels) of a light-emitting device and miniaturization of each display pixel pitch with reduction in the size of the light-emitting device. At the same time, demands such as increase of productivity and reduction in cost have also been increased.
The present applicants describe an example of a cross section of an evaporation mask in Patent Document 1 (Japanese Published Patent Application No. 2003-313654). In either cross-sectional structure of the evaporation mask disclosed in Patent Document 1, the vicinity of an opening of the mask is sharp. A tapered shape is given as an example of the cross-sectional structure of the evaporation mask.